WASHINGTON — President Donald Trump will get a second Supreme Court pick and the opportunity to cement conservative control of the court, with Justice Anthony Kennedy announcing Wednesday that he will retire July 31.

Democrats demanded a delay until after the November elections, as Republicans did in the final year of the Obama presidency. But without control of the Senate, they're not likely to get their way, a prospect that sent shudders to backers of abortion rights, gun control and a host of issues on which Kennedy has long been a moderating voice.

Kennedy, 81, has controlled the court's center for more than a decade. He was an appointee of Republican icon Ronald Reagan who ended up as a swing vote for much of his three decades on the nation's highest court, disappointing conservatives along the way.

His vote was crucial in high-profile cases involving affirmative action, gay rights, campaign finance and voting rights. He'll leave behind four liberal justices named by Democratic presidents and four conservatives named by Republicans.

That, said Texas Sen. Ted Cruz, means this vacancy "is an opportunity to really have a profound impact on the court, an impact on the court that could last for decades."

But Republicans hold a slim 51-49 majority in the Senate, and battle lines were quickly drawn.

Senate rules make it hard, if not impossible, for Democrats to delay confirmation, although they quickly demanded the seat stay open until after the November midterm elections, just as Republicans did when conservative Justice Antonin Scalia died in February 2016.

President Barack Obama nominated a well-regarded appellate judge, Merrick Garland. But Republicans refused to hold a confirmation vote, insisting on keeping the seat open until voters chose a new president.

Cruz was among the earliest advocates of that maneuver, and it paid off.

The Scalia vacancy opened nearly nine months before Election Day 2016. This one comes with the midterms only about four months away.

On Wednesday, Democrats argued that fair play requires keeping the Kennedy seat vacant until the November elections, when voters decide which party controls the Senate for the next two years.

"Our Republican colleagues in the Senate should follow the rule they set in 2016, not to consider a Supreme Court justice in an election year," Senate Democratic Leader Chuck Schumer said on the Senate floor. "Sen. McConnell would tell anyone who listened that the Senate had the right to advise and consent, and that was every bit as important as the president's right to nominate. Millions of people are just months away from determining the senators who should vote to confirm or reject the president's nominee, and their voices deserve to be heard now as Leader McConnell thought they should deserve to be heard then."

Justice Kennedy was the obstacle to moving further to the right on issues like abortion and affirmative action. But just as important, the fact that his vote wasn’t certain dissuaded conservative interest groups and justices from taking up a host of big issues. That all changes.

Potential candidates

Trump released a list of potential high court picks before he took office. The latest White House-issued list, from last November, includes 25 candidates. Utah Sen. Mike Lee and 24 judges, including Willett, were on it.

"It will be somebody from that list," Trump told reporters after Kennedy's announcement.

"We have no doubt that Donald Trump will select a dangerous nominee who will pledge to undo the progress we've made over the last decade and change the course of this country for a generation," he wrote in a fundraising email.

He noted that in the last week alone the high court upheld Trump's ban on travel from several majority Muslim countries, dealt a blow to public sector unions by ending mandatory dues, and upheld partisan gerrymandering — all by narrow votes.

"Everything we care about is on the line if we don't win this November," O'Rourke wrote. "Voting rights, civil rights and workers rights, healthcare and protections for those with pre-existing conditions; a woman's right to choose; LGBTQ equality; finally getting big money out of politics."

Groups that oppose abortion and groups that support LGBTQ rights alike offered little praise for Kennedy as he departs — reflecting the contentious areas in which he's impacted American society and jurisprudence.

.@joepojman: "We are very pleased that Justice Kennedy will retire from the Supreme Court, This is welcome news. Kennedy was the deciding vote in the Court's terrible decision in 2016 that struck down Texas' safety regulations for abortion facilities." #TXlege

The American people deserve to have a voice in the selection of their next Supreme Court Justice. Not 👏 a 👏 single 👏 nominee 👏 by the @realDonaldTrump admin should get a hearing OR a vote until after the November 2018 mid-term elections. #SaveSCOTUShttps://t.co/zUTWFwfe1V

Kennedy's influence

But Kennedy's influence in divisive cases was indisputable. "It was regular practice in close cases for entire briefs and oral arguments to be tailored just for him," said Chip Babcock, a Texas trial attorney.

Prominent on Trump's list are Judges Thomas Hardiman of Pennsylvania and William Pryor of Alabama, seriously considered for the seat eventually filled by Gorsuch, and Judge Brett Kavanaugh, who serves on the federal appeals court in Washington, D.C.

Kavanaugh served as a law clerk to Kennedy and then as a key member of independent counsel Kenneth Starr's team, which produced the report that led to President Bill Clinton's impeachment. In October, he dissented when his court ruled that an undocumented teen in federal custody should be able to obtain an abortion immediately.

"Washington is already gearing up for Red vs. Blue blood sport," Nebraska Sen. Ben Sasse, a Republican, said, predicting a nasty confirmation battle with the court's direction at stake. "Americans ought to aim higher because, as Justice Kennedy put it, 'our system presumes that there are certain principles that are more important than the temper of the times."

McConnell, the Senate Majority Leader, set a marker that no matter how much Democrats dislike the president's nominee, he won't tolerate a blockade.

"We will vote to confirm Justice Kennedy's successor this fall," he said on the Senate floor.

Sen. John Cornyn of Texas, the deputy GOP leader, also insisted on moving forward.

Abortion as flash point

Abortion is a likely flash point in the nomination fight. Kennedy has mainly supported abortion rights. Trump has said he would choose justices who want to overturn the landmark abortion rights case of Roe v. Wade.

Republicans hold a bare 51-49 majority in the Senate, although that includes the ailing Sen. John McCain of Arizona.

The court fight will loom over the midterm elections. Activists across the spectrum have long used such battles as a focal point for fundraising and to energize voters.

Tony Perkins, president of the Family Research Council, a group of religious conservatives, said the court fight "will turbo charge this fall's election. In a closely divided U.S. Senate, every vote matters. If values voters needed a reason to engage in this election cycle — they certainly have it now."

Regardless of who replaces him, Kennedy's departure bodes massive change for the high court.

He has sided with the liberal wing on abortion rights and, in some cases involving race, the death penalty and the rights of terror suspects detained at the Guantanamo Bay naval base. He has written all the court's major gay-rights decisions, including the 2015 ruling that declared same-sex marriage is a constitutional right nationwide.

He has sided with conservatives when the court ended the 2000 presidential election recount in favor of George W. Bush, and on protecting gun rights, limiting regulation of campaign money, and gutting a key provision of the landmark Voting Rights Act.

Several former law clerks said that Kennedy would prefer to be replaced by a Republican. If Democrats capture the Senate in November, they could block a conservative Trump nominee.

But few obstacles seem to stand in the way of a confirmation before the court reconvenes in October. Republicans changed the rules during Gorsuch's confirmation to wipe out the main delaying tactic for Supreme Court nominees, the filibuster, and the need for 60 votes to defeat it.

Court watchers had speculated on which justice would retire next. Wednesday was the final day of the court's current term. Kennedy issued a statement after the final decisions were handed down, rather than announcing his retirement from the bench, as justices often do.

Justice Ruth Bader Ginsburg is 85. Justice Stephen Breyer is 79. Both are Democrats, and by all accounts, neither intends to retire while Trump is president.